A UV absorber, 5,5'-methylenedisalicylic acid (MDSA), has been intercalated into a ZnAl-NO3 layered double hydroxide (LDH) by an ion-exchange method. After intercalation of MDSA, the basal spacing in the LDH increased from 0.90 to 1.53 nm, suggesting that the MDSA anions were arranged in the interlayer galleries of ZnAl-MDSA LDH as a tilted monolayer arrangement of dianions. Infrared spectroscopy and thermogravimetry and differential thermal analysis (TGA-DTA) Curves revealed the presence of a complex system of supramolecular host-guest interactions. The thermal stability of the intercalated UV absorbent was investigated by TGA-DTA, which showed that the thermostability was markedly enhanced after intercalation into the LDH host. After addition of 1 wt % ZnAl-MDSA LDH to polypropylene (PP), the resistance of the polymer to UV degradation was significantly improved.